In the case of the automatic placement of surface mounted components, so-called SMD components, on printed circuit boards, the components are provided via various types of feed devices. The provision of taped components have a particular importance in this case. The form of delivery in a tape (cf. DIN IEC 286, September 1987) is particularly convenient for automation since the components are already separated and the packaging in a tape ensures a high level of protection against confusion. In the individual feed devices for taped components, the tapes with the components are unwound from a tape spool and are then fed to a removal position for the components. In the removal position, the components are then held by the suction pipette of a placement head and are set down in the predetermined placement position on a printed circuit board (cf. EP-A-0 013 977 and EP-A-0 016,368). In order to provide the components in the correct removal position, the tape is driven with the aid of a transport wheel whose transport pins engage in the transport holes in the tape. Since the SMD components are of smaller and smaller size and, in addition, the aim is to achieve placement performances which are as good as possible, feed devices for taped SMD components are subject to the following main requirements:
positioning accuracy which is as high as possible;
transportation times which are as short as possible; and
tape transport optionally for a 4 mm pitch and a 2 mm pitch of the component compartments in the tape.
A feed device which satisfies these requirements is known from EP 0 589 275 B1. Modem automatic component replacement machines are achieving increasing cycle frequencies for picking up and fitting components. If, for example in the case of a revolver or turret placement head, a number of suction pipettes can be filled with identical components, and the latter must be taken from the tape as quickly as possible, in order to approach the pick-up performance of the placement head.
Furthermore, DE 37 10 310 A1 discloses a feed device for components, in which a magnetically operable catch engages in a tooth system on a supply spool, and in each case allows this to move onward through one feed cycle.
The invention is based on the object of speeding up the process of removing components from the component tape even further.
This object is achieved by an improvement of a feed device for components which are mounted in component compartments on a tape at a pitch spacing, the tape having transport holes arranged at the pitch spacing, the device including a transport wheel having transport pins engageable in the transport holes of the tape, at least one drive motor for driving the transport wheel in such a manner that a whole number of revolutions of the drive motor to an annular position produces a transport movement of the tape which corresponds to one pitch spacing, a sensor for detecting the number of revolutions of the drive motor, a stop surface which is connected to the rotor of the drive motor and is positioned transversely with respect to a radial direction, a mechanical stop which acts against the stop surface and stops the rotation of the drive motor in the annular position corresponding to one complete revolution of the drive motor to shift the tape one pitch spacing. The improvement comprises an active control element to lift the stop off the stop surface at the start of the feed rotation of the drive motor and to push the stop into a movement path of the stop surface before the end of the desired complete rotation so that the rotary movement can be continued toward the annular position until the stop position on the stop surface is reached.
The active stop now allows the position of the drive to be fixed directly during forward movement, without any reversal of the rotation direction, with the corresponding loss of time, being required for this purpose. The stop can be operated, for example, by a pneumatic control element, as is used, for example, for opening and closing a pick-up window for the components. If it is operated, for example, in synchronism with the pick-up window, there is no need for the stop to have its own control valve.
A development of the invention has the mechanical stop in the form of a radially movable pin and the stop surface is on a stop disk and this development makes reliable implementation of the mechanical stop possible at a low cost.
An exemplary embodiment of the invention is described in more detail in the following text, and is illustrated in the drawings.